Many vehicular fuel tanks have a vapor vent consisting simply of a small tube pushed through the top of the tank to project downwardly into the tank to the desired fuel fill level, at which point the tube is simply cut off flush. With this type of construction, the tank will vent vapors until the fuel level reaches the bottom of the tube, at which point the vent becomes blocked and the resulting pressure buildup in the fuel pipe shuts off the fuel nozzle in a known manner. Neither liquid fuel nor fuel vapors can now vent, and the fill level of the fuel is fixed. Expansion of the fuel due to a temperature rise now could cause liquid fuel to be expelled out the fill pipe if the cap is suddenly removed, which would be undesirable.
Other constructions have a vapor vent that is located near the top of the tank above the normal fuel level that is maintained open at all times, and depend upon some other device external to the vapor vent assembly to control the fill level of the fuel.
The invention provides a vapor vent assembly that in itself controls the fill level of the tank to the proper level that can be higher than the bottom of the vent assembly, and also provides means to minimize any expulsion of liquid fuel out of the fill pipe upon removal of the cap after a temperature rise expansion of the fuel or rollover of the vehicle/tank.